In the experiments of a water storage cylindrical shell, excited by a horizontal external force of sufficient large amplitude and high frequency, it has been observed that gravity water waves of low frequencies may be generated. This paper intends to investigate this phenomenon in order to reveal its mechanism. Considering nonlinear fluid–structure interactions, we derive the governing equations and the numerical equations describing the dynamics of the system, using a variational principle. Following the developed generalized equations, a four-mode approximation model is proposed with which an experimental case example is studied. Numerical calculation and spectrum analysis demonstrate that an external excitation with sufficient large amplitude and high frequency can produce gravity water waves with lower frequencies. The excitation magnitude and frequencies required for onset of the gravity waves are found based on the model. Transitions between different gravity waves are also revealed through the numerical analysis. The findings developed by this method are validated by available experimental observations.
The porous aerostatic conveyor bearings are used to feed large substrates such as the flat panel display glass sheets and the silicon wafers by supporting them with compressed air in a non-contact condition. Due to unevenly distributed pressure in the air film between the substrate and the porous aerostatic conveyor bearing, the soft substrate often deforms and tilts on the bearing pad during the feeding process. In order to investigate the pressure distribution in the air gap, the CFD software, FLUENT, was employed to simulate the operation of the porous aerostatic conveyor bearing during the feeding process. In addition, the load capacity of the conveyor air bearing was calculated. The results show there is low vacuum pressure around the air discharge holes. The high pressure above the air supply holes forms two paraboloidal distributions in the air film. For design modification, the air supply and the air discharge holes need to be rearranged and/or relocated to improve the pressure distribution in the air film for more stable feeding of the substrate.
The effects of the rotating speed of the spindle, the number of the porous medium inserted into the partially porous aerostatic journal bearing and the thickness of the bearing gap on the characteristics of the bearing such as the pressure distribution, the load carrying capacity and the stiffness of the bearing were studied. Based on the finite volume method and the pressure-velocity coupling scheme of the SIMPLE algorithm with the standard k-ε turbulent model, the CFD software was used to solve the Navier-Stokes equations to calculate the pressure field in the bearing gap. The computed results revealed the faster the spindle rotated, the higher the gap pressure. As the gap thickness increased, the gap pressure, the load carrying capacity and the stiffness of the bearing decreased. The more the porous inserts, the higher the gap pressure and the load carrying capacity, but the less the bearing stiffness would be.
This study investigated the effect of the spindle speed on pressure distribution in the air gap and the load carrying capacity of a porous aerostatic annular thrust bearing. Based on the finite volume method and the pressure-velocity coupling scheme of the SIMPLE algorithm with the standard k-ε turbulent model, a CFD software was used to solve the Navier-Stokes equations to calculate pressure and velocity of the air flow. The results revealed there were positive pressure zones and vacuum pressure zones in the air gap between the thrust disk and the bearing. Under the same spindle speed, the pressure difference between the positive peak and the negative peak in the case of incompressible air was greater than that in the case of compressible air. The averaged pressure on the surface of the thrust disk with compressible air flow was higher than that with incompressible air flow. So was the load carrying capacity of the bearing, which increased when the spindle rotated faster.
This article points out the views from “Software manufacturing Instrument” to “Software manufacturing Everything” and to “software rebuilds, rules, and defines the world ” , as well as shows the agreement and support at home and abroad to “Software manufacturing Everything”. Software is the crystallization of human’s intelligence, and the new wave of software has become the main competitive force of mainstay industry. This article also provides the consequence that the DASP of COINV measured , an the accuracy reached 10^(-17).
A new method for automatically and fast self-detection of the main indexes of radial grating is proposed and achieved, basing on digital sampling and digital processing, ugh-multiple digital subdivision and improvement of the quality of signal lead to high detection precision. separately detect the indexes. With the new method, high-rn..iltiple : TillS PROJUCT IS SUPPORTED BY TIlE NATURAL SCIENCE FUNDAT ION OF CII INA.
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